Nasal Flow Simulation Using Heat and Humidity Models

Abstract

The nasal cavity performs several important functions for the inhaled air, such as temperature and humidity adjustments. Although it is necessary to obtain velocity, temperature, and humidity distributions during inhalation in order to understand the nasal cavity's functions, it is difficult to measure them noninvasively in the nasal cavity. Therefore, we have continued to study nasal flow simulation with heat and humidity transport. In such a simulation, the governing equations include a continuum equation and the equations describing momentum, energy, and water transport. The temperature and humidity of the inhaled air are adjusted by heat and water exchange on the nasal cavity wall's surface. Therefore, in the simulation, these roles of the wall in the energy and water transport equations were included as the boundary conditions. Although in related studies of nasal flow simulation with heat and humidity transport, the nasal cavity wall's surface temperature and humidity were constant, here they were treated as degrees of using Newton's cooling law. A flow including temperature and humidity in a realistic human nasal cavity shape was simulated. The simulation results agreed well with the measurements reported by Keck at al. Therefore, this study concludes that our model can simulate the heat and humidity exchange occurring in the nasal cavity. In addition, it was found that the temperature and humidity adjustment functions worked effectively in the front and narrow regions of the nasal cavity.

Minor contributions of the maxillary sinus to the air-conditioning performance in macaque monkeys

“…A steady simulation is reasonable under a normal breathing frequency and flow rate in the resting stage in humans (Swift and Proctor, 1977;Hornung et al, 1987;Hahn et al, 1993;Schreck et al, 1993;Keyhani et al, 1995;Doorly et al, 2008;Kumahata et al, 2010;Hanida et al, 2013). The maximum Reynolds numbers ranged from 85 to 555 at the external nostrils in the subjects used here, calculated with estimates of the inhaled air velocity in the resting stage.…”

“…Voxel data for the nasal cavity and MS anatomy were reconstructed from the CT scans (Kumahata et al, 2010;Hanida et al, 2013). The black areas represent air filling the nasal cavity, and the MS was extracted first using Avizo 7 (FEI Visualization Sciences Group, Hillsboro, OH, USA) based on a threshold of brightness, and the voxel data were reconstructed.…”

“…, which is the thermal conductivity of water (Lervik et al, 2010), because a liquid mucous membrane is assumed in the model used here (Kumahata et al, 2010;Hanida et al, 2013). T S is determined by Q total , which comprises Q memb and Q latent .…”

“…This feature is believed to have arisen independently in these lineages as the paranasal sinuses, including the MS, were lost once in a common ancestor of extant Old World monkeys (Rae et al, 2002). The performance of the air conditioning depends mainly on how the air flows through the nasal cavity (Lindemann et al, 2004;Naftali et al, 2005;Kumahata et al, 2010;Hanida et al, 2013). The structures in the nasal cavity, especially in its anterior region, have major effects on the air-conditioning performance in humans (Lindemann et al, 2004;Naftali et al, 2005;Kumahata et al, 2010;Hanida et al, 2013).…”

“…The performance of the air conditioning depends mainly on how the air flows through the nasal cavity (Lindemann et al, 2004;Naftali et al, 2005;Kumahata et al, 2010;Hanida et al, 2013). The structures in the nasal cavity, especially in its anterior region, have major effects on the air-conditioning performance in humans (Lindemann et al, 2004;Naftali et al, 2005;Kumahata et al, 2010;Hanida et al, 2013). Nevertheless, in macaques, the MS topological differences suggests it has a functional role in air conditioning (Márquez and Laitman, 2008), and the airflow in and out of the MS could affect the airflow within the nasal cavity, which has some topological differences from that in humans.…”